. >> paleontologists henry sadler and derrick demeter finding a once in a millennium mammoth bone while river. >> maybe eight feet at the deepest in this little area. not crazy deep, but pitch-black, trees everywhere. you're bumping into logs. >> i can't see henry right next to me. >> reporter: the guys choosing this spot because they'd had luck fossil hunting before. >> this is one of the pieces i'd found recently up there. >> so they knew what they were up against. >> normally we wouldn't do the peace river this time of year because that's when the gators and they start to get a little - bit more aggressive. >> reporter: are you kidding? >> yeah. >> reporter: despite those odds, henry striking fossil-hunting gold in the water. >> i'd climbed over a fallen palm tree. the next thing i put my hand on was the mammoth bone, and i knew instantly. >> reporter: the guys spending the next half hour digging out the rest. >> iind of have to walk on the bottom carrying this 60-pound bone to the shore. >> we got ourselves a mammoth leg bone. >> reporter: the mammoth leg bone somewhere between 1000

. >> reporter: amateur paleontologists henry sadler and eric demeter finding a mammoth bone while divingright next to me. >> reporter: the guys choosing this spot because they've had luck fossil hunting there in the past. >> this is one of the teeth i found pretty recently over there. >> reporter: so they knew what they were up against. >> normally we wouldn't do the peace river this time of year because because usually that's when gators are starting their mating season and start to get a little bit more aggressive. >> are you kidding? >> yeah, yeah. >> reporter: despite those odds henry striking fossil hunting gold in the water. >> i climbed over a fallen palm tree. the next thing i put my hand on was the mammoth bone and i knew instantly. >> reporter: the guys spending the next half hour digging out the rest. >> so i just kind of have to walk on the bottom carrying this 60-pound bone to the shore. >> reporter: the mammoth leg bone somewhere between 10,000 and 2.6 million years old. >> really makes me wonder what it was like to be back in this time period when we had these mega, big an